Magnetic implants used to treat ‘dancing eyes’

26 June 2017

A
research team has successfully used magnets implanted behind a person’s
eyes to treat nystagmus, a condition characterised by involuntary eye
movements.

The case study, published in Ophthalmology and
led by UCL and University of Oxford academics, described the
implantation of a newly developed set of magnets in the socket beneath
each eye of one patient with nystagmus. It’s the first description of a
successful use of an oculomotor prosthesis, or an implant that controls
eye movement.

“Our study opens a new field of using magnetic implants to
optimise the movement of body parts.” Dr Parashkev Nachev (UCL
Institute of Neurology), the lead author of the paper.

Nystagmus involves a rhythmic oscillation, or flickering of
the eyes, and is sometimes called ‘dancing eyes.’ It often results in
oscillopsia, the perception of constant movement of the visual field.
The condition affects close to 1 in 400 people and can be both
intrinsically disabling and cause reduced visual acuity.

“Nystagmus has numerous causes with different origins in
the central nervous system, which poses a challenge for developing a
pharmaceutical treatment, so we chose to focus on the eye muscles
themselves. But until now, mechanical approaches have been elusive
because of the need to stop the involuntary eye movements without
preventing the natural, intentional movements of shifting gaze.”
Dr
Nachev.

The patient who underwent the procedure developed nystagmus
refractory to conventional treatment in his late 40s due to Hodgkin’s
lymphoma, with great impact on his life, including loss of employment.
His difficulties prompted the research team to investigate the use of an
oculomotor prosthesis which had previously been described
theoretically, but not confirmed in practice.

The research team developed a prosthesis involving one
magnet which is implanted on the orbital floor (the bone at the bottom
of the eye socket), interacting with a smaller magnet sutured to one of
the extraocular muscles, which control the eye’s movement. The magnets
are encased in titanium, which can be safely embedded internally, thus
enabling the magnetic force to be applied without causing any damage.

“Fortunately the force used for voluntary eye movements is
greater than the force causing the flickering movements, so we only
needed quite small magnets, minimising the risk of immobilising the
eye.” Professor Quentin Pankhurst (UCL Medical Physics &
Biomedical Engineering), who led the design of the prosthesis.

Before implantation, the magnets were tested while attached
to a custom-made contact lens. After that was shown to be successful,
the magnetic prostheses were implanted in two separate sessions, one for
each eye, by Professor Geoff Rose and Mr David Verity at Moorfields Eye
Hospital. The patient recovered quickly from both procedures, and
reported that the oscillopsia improved, although he has a degree of
double vision, a symptom which he had developed before the nystagmus.

Testing showed that his overall visual acuity was
substantially improved, and there has been no negative impact on his
functional range of movement. Over four years of follow-up reports, the
patient’s symptoms have remained stable and he has managed to return to
paid employment and reports substantial improvement in daily activities
such as reading and watching television.

“While the exact neural mechanisms causing nystagmus are
still not fully understood, we have shown that it can still be corrected
with a prosthesis, without needing to address the neural cause. What
matters here is the movement of the eye, not how it is generated.” Professor Christopher Kennard (University of Oxford), who co-led the
study.

The researchers caution that their prosthesis wouldn’t be
effective for everyone with nystagmus, as magnetic implants are not
suitable for patients who require regular MRI scans, and further
research needs to be done to understand in which patients the prosthesis
would be most helpful.

The researchers are currently recruiting for a
larger study, led by Professor Rose at Moorfields Eye Hospital, and
funded by the National Institute for Health Research (NIHR). The study
benefits from a collaboration with the nystagmus patient support group,
the Nystagmus Network.

The study benefited from funding from the NIHR’s National
Programme for New and Emerging Applications of Technology, the NIHR
Biomedical Research Centres at UCLH, Moorfields Eye Hospital and Oxford,
and Wellcome.